抄録
1. In the present study, the author investigated the development of the so-called “yuzuhada” disorder of the fruit of Nijisseiki pear trees, with reference to daily change of fruit growth accom-panied by a deficiency of water in leaves due to natural and artificial aridity of soil at a certain growing period.
2. The degree of water deficiency in leaves as expressed in the percentage of saturated water content minus water content at a certain time of a day was always higher in the disordered trees than in the healthy trees, and this tendency was also found even when irrigated.
3. The disordered trees always exceeded the healthy trees in the osmotic pressure of leaves, and this relation was also the same with the difference of the osmotic pressure between leaves and fruits, the value of which by the disordered
trees often reaching to more than five atm. at 6 p. m. on a hot dry summer day.
4. During the period from May to August, when the soil was kept arid, the treated at the end of June or July, produced the disordered fruit and the damage was more conspicuous in the July case.
5. In the daily change of growth, the fruits which would suffer from “yuzuhada”, coincided with the fruits which were of artificial water deficiency. Consequently, it seems that “yuzuhada” would develop as the result of the abnormal shrinkage due to the natural water deficiency in the tissue.
6. Nijisseiki pear grafted on Pyrus betulaefolia got less “yuzuhada” disorder than those on P. serotina, but even the former also were damaged when dried for a long period in summer.
